This application claims the right of priority of German patent application No. 199 55 858.2 filed Nov. 20, 1999, the disclosure of which is incorporated herein by reference.
The invention relates to an axial face seal, particularly a running gear seal, including a sliding ring and/or a counter-ring, which has a sliding surface and a conical circumferential surface outside the sliding surface for accommodating at least one elastic roll body.
Running gear seals are frequently used in drive shafts of construction machinery, e.g. hydraulic excavators. These machines are subjected to high wear because of dust, sand, mud or rocks. Running gear seals as a rule consist of angular sliding rings and/or counter-rings, wherein one of the legs of the angular profile holds a sealing member. The space between the sliding ring and/or counter-ring and the sealing member is filled at least in part with dirt during the operation of the construction machine. As a result of drying and hardening, this mud can highly obstruct the freedom of movement for the seal. In some circumstances, this can lead to an early failure of the seal.
A sliding ring and/or counter-ring for an axial face seal is known from German Patent Document No. A 31 41 512, which can be used in particular under relatively high pressures. The axial face seal is provided with a conical circumferential surface for accommodating at least one elastic roll body, wherein the roll body in the assembled state is located between the conical circumferential surface and an also conical, corresponding circumferential surface of a machine part or housing part that holds the sliding ring and/or counter-ring. At least one other secondary seal extends between the sliding ring and/or counter-ring and the corresponding machine part or housing part. The sliding ring and/or counter-ring is designed to have an approximately L-shaped profile, wherein the radial leg of the L-shaped profile forms a sliding surface, which can be provided at different radial heights of the leg, depending on the design of the sliding ring and/or counter-ring.
In order to move large amounts of material, presentday construction machines are designed to have larger and larger dimensions to permit economic material transport. The running gear seals for large machinery of this type must therefore have correspondingly large dimensions to provide an effective seal for the axles and other units. The equipment manufacturer furthermore expects the seal to meet particularly high requirements concerning the service life.
It is the object of the invention to provide an improved axial face seal, so that on the one hand the high service life requirements for the seal are met and, on the other hand, the repair costs and costs for producing the seal itself can be kept low.
The axial face seal may be a running gear seal having a sliding ring and/or counter-ring having a sliding surface and a supporting portion with a conical circumferential surface outside the sliding surface for accommodating at least one elastic roll body.
According to the invention, this object and others to become apparent as the application progresses, are achieved by providing a sealing leg of the sliding ring and/or counter-ring, which has the sliding surface, with an extended region that extends past the supporting portion. In a further aspect, the extended region of the sealing leg is reinforced.
The design of the sliding surface region is particularly important for achieving an especially long service life, wherein according to the invention the sliding surface width in radial direction can be used as wear reserve.
By extending the sealing leg with the sliding surface of the sliding ring and/or counter-ring, this leg is provided with a T-shaped contour. However, if subjected to higher stress, this contour will have a tendency to be distorted especially on the inside third because of the axial forces that must be controlled. The design according to the invention therefore calls for reinforcing this region. Owing to the fact that a cast, solid profile may be undesirable for cost reasons, various other options for creating the necessary stiffness may be employed while avoiding a solid profile and still keeping the material costs as low as possible.
Sections where the material is thickened in the form of projections or shoulders are viewed as suitable embodiments. Since a material thickening along the entire circumference may not be desirable, these sections can have optional dimensions, so that a plurality of profiles forming material thickenings are provided, distributed in circumferential direction.
A preferred alternative provides for projections extending between the extended sealing leg of the sliding ring and/or counter-ring and the leg that accommodates the roll body.
According to another aspect of the invention, the shaped projections extend between the free ends of the extended sealing leg on the one hand and the leg holding the roll body on the other hand. With respect to the production, the shaped projections can be designed as fins that are molded onto the inside circumferential area of the sliding ring and/or counter-ring.
By virtue of the above features, the complete profile of the sliding ring and/or counter-ring is provided with the required stiffness and thus also the freedom from distortion for all stress conditions and material use is reduced to an acceptable minimum.
The evenness of the sliding surface is ensured even if the location of the sliding surface has moved to the radial inside region of the sealing leg because of wear.